The present invention relates to a method of determining if a material has been subjected to an energy source. More particularly, the present invention relates to methods which allow the inspection of one or more substrates to determine whether the substrate has been subjected to an energy source such as that used for welding or fusing of substrates. The invention includes the use of light emitting materials such as luminescent dyes and pigments such as a fluorescing agents, phosphorescing agents, visible dyes, or the like, which can be locally applied to the substrate.
Medical devices such as catheter devices, are typically comprised of a number of components, some of which are sealed together using adhesives, thermal fusion, laser welding, and so forth.
Fusion, laser or thermal bonding are becoming more popular because the bonds typically achieved with these methods in contrast to adhesive bonds, are superior in strength. Furthermore, the use of adhesives adds to the thickness of the catheter and increases the rigidity at the region of the bonds.
It is of significant importance in the manufacture of catheter devices to be able to achieve a good seal when bonding the various components together regardless of the method used. This is, however, often a difficult task due to the very small size of these medical devices.
One such method of monitoring the performance of the bond or seal achieved, is to use tensile and burst testing. However, this involves the destruction of the substrates.
For laser and thermal welding, the surface of the material may change, in some cases, from a shiny to a matte finish. It has been hypothesized that this may be indicative of the bond strength. However, tensile and burst testing are still required to ultimately determine bond performance.
Providing a bond through fusion or laser welding of materials including polymeric and metallic materials, is becoming a popular alternative to adhesive usage. It is also, consequently, desirable to have a method by which bonds can be inspected and performance ascertained without destroying the bonded substrates because destruction of the substrates can be of detriment economically, and in any event, waste is undesirable.
Luminescent (including fluorescent and phosphorescent) markers have been used for a wide variety of applications in science, medicine and engineering. For instance, the incorporation of fluorescent compounds into coating compositions is known. For example, the addition of fluorescing agents to coatings is now used to determine thickness of release coatings. Fluorescing agents added to coatings will emit radiation of an intensity that is proportional to the coating thickness. Sensors can then be used to produce an electronic signal proportional to the emission intensity. Further, a controller may be installed on manufacturing equipment to which uses this signal to make mechanical adjustments to the coating machine in order to maintain constant coating thickness.
U.S. Pat. No. 5,310,604 describes a method for monitoring the coating weight, uniformity, defects or markings present in a coating of a composition applied to a substrate by using an effective amount of a uv-escer in the coating composition.
U.S. Pat. No. 6,060,169 describes a material and a method for forming a tamper-indicating identification coating.
U.S. Pat. No. 6,080,450 describes the incorporation of a high concentration of luminescing agent, e.g. fluorescing agent, into an actinic radiation, e.g. UV, curable polymerizable acrylate formulation using a phosphine oxide photoinitiator to enable the curing, the luminescing or fluorescing agent present to facilitate and enhance the efficiency of evaluation of the cured deposit by utilizing its fluorescent response.
Furthermore, the incorporation of fluorescent compounds into coating compositions to provide a non-destructive method for inspection of the quality, consistency, and so forth of the coating is discussed in U.S. Pat. Nos. 6,080,450 and in 5,310,604.
There remains a need in the art, however, for an easy method of monitoring and inspecting a bond or seal formed by thermal fusion or laser welding.
The present invention allows for determination of whether or not a source of energy has been applied to a substrate. The present invention relates to a method of manufacturing a medical device including the steps of selecting a first substrate, selecting a light emitting material having a first emission spectrum and a second emission spectrum different from said first emission spectrum upon subjection to a source of energy, applying the light emitting material to a polymeric substrate, and applying a predetermined energy source to the substrate sufficient to change the first emission spectrum of the light emitting material to the second emission spectrum. The second emission spectrum may constitute a non-emission.
The method can also include the step of detecting the second emission spectrum on the substrate. The second detected emission spectrum may be utilized to indicate the receipt by the substrate of a predetermined energy dosage. The first substrate may be joined to a second substrate before applying the predetermined energy source.
In one embodiment of the present invention, the predetermined level of energy applied may be that required to alter the physical properties of the polymeric substrate(s).
In another aspect, the present invention allows for nondestructive observation of a joint between a polymeric substrate and a second substrate such as in the case where the substrates have been joined by fusion or welding.
The present invention, in another aspect, can provide a method of detecting the optimal temperature for welding or fusing a first substrate and a second substrate, at least one of which is polymeric. The method includes the steps of providing a first substrate and second substrate of the same or a different material wherein at least one of the first, the second substrate, or both, is polymeric. The light emitting material of the present invention is applied to the substrate is applied to the substrate at a location where the first substrate and the second substrate will be joined. The light emitting material has a first emission spectrum that changes to a second, different emission spectrum upon exposure to a predetermined energy source. The first and second substrates may be joined by welding or fusing.
The light emitting material is selected so that the first emission spectrum of the light emitting material changes to the second emission spectrum when the predetermined source of energy required for welding has been supplied to the welding site. The predetermined source of energy may be a specified temperature, or it may be a specified wavelength, and so forth. In laser welding, for instance, at a given wavelength, the polymeric substrate is actually heated to a temperature that allows for welding.
In this aspect of the invention, the method allows for a means of detecting when the temperature for welding various polymeric materials has been achieved by incorporation of a light emitting material composition with a known emission spectrum at the interface of the bond. The light emitting material composition will emit energy of a given wavelength when exposed to a particular predetermined source of energy.
In one particular embodiment of the present invention, the light emitting material emits energy in the fluorescent region. Upon application of a predetermined energy source, the first emission spectrum of the light emitting material changes to the second emission spectrum. This change may be a shift from one fluorescent emission spectrum to another fluorescent emission spectrum, or the light emitting material may stop fluorescing altogether.
For instance, a fluorescent dye may be selected wherein the first fluorescent emission spectrum changes upon exposure to a source of energy that heats the substrate such as thermal energy, or a laser. The first fluorescent emission spectrum changes to a second emission spectrum upon achieving temperatures in excess of 100xc2x0 C. This change may be in the fluorescent range, or the second emission spectrum may be in a different wavelength range altogether.
In the case of thermal welding applications, for instance, the light emitting material may be selected based on the melting temperature of the polymeric substrate being welded, as well as to the predetermined energy source. In this instance, the emission spectrum of the light emitting material will desirably change at a temperature that is at or above the melting temperature of the polymer, for instance. Optionally, the light emitting material may respond and its emission spectrum change at the wavelength at which a laser is applied to weld the polymeric substrate(s).
The light emitting material thus responds to different wavelengths of energy supplied, or to different temperatures, for instance.
In this embodiment, the method of the present invention therefore allows for easy visual or instrumental inspection of welded joints. The areas that are exposed to the desired temperature or wavelength, for example infrared, ultraviolet, and so forth, will respond by a change in the emission spectrum or color of the light emitting material, indicating that the joint has reached the temperature or wavelength for an optimum seal.
The method of the present invention finds particular utility in the medical device art, in particular for intraluminal medical devices such as catheter delivery devices.
It is of importance in the manufacture of medical devices, in particular catheter delivery devices, that good seals between parts are achieved. For instance, when bonding a dilatation balloon to a catheter tube or shaft, if a tight seal is not achieved, inflation fluid may leak from the seal, and the desired pressure for inflation may not be achievable. The present invention therefore provides an easy and efficient way of monitoring the quality of the seal.